Rhodium complexes 2,2 -bipyridyl

Systems which fulfil these conditions are tris(2,2 -bipyridyl)rhodium complexes [63] and, more effectively, substituted or unsubstituted (2,2 -bipyridyl) (pentamethylcyclopentadienyl)-rhodium complexes [64], Electrochemical reduction of these complexes at potentials between — 680 mV and — 840 mV vs SCE leads to the formation of rhodium hydride complexes. Strong catalytic effects observed in cyclic voltammetry and preparative electrolyses are... 

A common class of mediators, which fulfill these requirements, are rhodium complexes (e.g., tris(2,2 -bipyridyl)- and substituted or nonsubstituted (2,2 -bipyridyl) (pentamethylcy-clopentadienyl)-rhodium complexes). This regeneration system has been efficiently applied in electroenzymatic reduction of pyruvate to D-lactate and the reduction of 4-phenyl-2-butanone to (S)-4-phenyl-2-butanol [1]. In an electrochemical membrane reactor, NADH was... 

Very efficient reduction of NAD(P) with formate catalyzed by cationic rhodium complexes. /. Chem. Soc. Chem. Commun., 1150-1151 (d) Franke, M. and Steckhan, E. (1988) Tris(2,2 -bipyridyl-5-sulfonic add) rhodium(III), an improved redox catalyst for the light-induced and the electrochemically initiated enzymatic reduction of carbonyl compounds. Angeiv. Chem., Int. Ed., 27, 265-267 (e) Grammenudi, S., Franke, M., Vogde, F., and Steckhan, E. (1987) The rhodium complex of a tris(bipyridine) ligand - its electrochemical behavior and frmction as mediator for the regeneration of NADH from NAD. /. Ind. Phenom. Macrocycl. Chem., 5,695-707 (f) Hollmaim, F., Kleeb, A., Otto, K., and Schmid, A. (2005)... 

Fig. 17. Electroenzymatic reduction of 4-phenyI-2-butanone catalyzed by HLADH with in-situ indirect electrochemical regeneration of NADH using a Cp (2,2 -bipyridyl)aquo rhodium(III) complex as mediator...

The preparation of bis(bipyridyl) (702) and bis(phenanthroline) cobalt(III) complexes (576) has been the subject of a number of papers. Interest centers on the possibility of cis-trans isomerism in these complexes, since it would seem that the close approach of the 6,6 -(bipyridyl) and 2,9-(phenanthroline) protons in the trans complex would make this stereochemistry unattractive for central ions such as co-balt(III), rhodium(III), or iridium(III). Cis complexes are well established, but a violet compound claimed to be anionic cobalt(II) species (21, 573, 591). 

With transition metal complexes (typically rhodium compounds), it is possible to functionalize pyrrole and to obtain active electrodes for the hydrogenation of ketones. An example showing the behaviour of a film of poly(pyiTole-Rh(lll)bipyridyl) is the reduction of cyclohexanone into cyclohexanol with a chemical yield of 79% [110], This molecular electrode is also suitable for the reduction of water in hydrogen, Electrocatalytic hydrogenation of other ketones, unsaturated ketones or aldehydes, has been studied recently [174-176], These hydrogenation reactions are performed in an aqueous medium and the modified electrodes are obtained after electropolymerization of pyrrole substituted 2,2 -bipy-ridine or 1,10-phenanthroline complexes of Pd(Il) or of Rh(Ill). More precisely, with the Pd(ll) complex... 

Apart from the phosphine complexes described, the hydrogen transfer activity of several other derivatives has also been investigated. Among them rhodium, and iridium bipyridyl, and phenanthroline compounds displayed the highest catalytic activity with turnover numbers up to 900 cycles/min. Reducing unsaturated ketones, first the C=C double bond is saturated, but the successive reduction of the C=0 group is comparable in rate with that of the olefinic bond. 

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